The present invention consists of a radiation delivery catheter that is compatible with the transfer device described in the above-identified patents and patent applications that are referenced herein. The radiation delivery catheter is a component of a system designed to reduce the frequency of restenosis (re-blockage) in coronary arteries after balloon angioplasty or other interventional procedure. The catheter is inserted into the patient using a guide wire and guide catheter previously positioned in the patient for the balloon angioplasty procedure; the catheter is then connected to the transfer device and the distal tip of the catheter is guided to the treatment site in the artery. Radioactive treatment elements are hydraulically or pneumatically delivered from the transfer device to the treatment site, and after the appropriate dosage has been delivered, the sources are returned into the transfer device by reversing direction of the fluid flow.